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A227310
G.f.: 1/G(0) where G(k) = 1 + (-q)^(k+1) / (1 - (-q)^(k+1)/G(k+1) ).
13
1, 1, 0, 0, 1, 0, 0, 1, 0, 1, 1, 0, 2, 1, 1, 3, 2, 3, 4, 4, 6, 7, 8, 11, 13, 16, 20, 24, 31, 37, 46, 58, 70, 88, 108, 133, 167, 204, 252, 315, 386, 479, 594, 731, 909, 1122, 1386, 1720, 2124, 2628, 3254, 4022, 4980, 6160, 7618, 9432, 11665, 14433, 17860, 22093, 27341, 33824, 41847, 51785, 64065, 79267
OFFSET
0,13
COMMENTS
Number of rough sandpiles: 1-dimensional sandpiles (see A186085) with n grains without flat steps (no two successive parts of the corresponding composition equal), see example. - Joerg Arndt, Mar 08 2014
The sequence of such sandpiles by base length starts (n>=0) 1, 1, 0, 1, 0, 2, 0, 5, 0, 14, 0, 42, 0, ... (A097331, essentially A000108 with interlaced zeros). This is a consequence of the obvious connection to Dyck paths, see example. - Joerg Arndt, Mar 09 2014
a(n>=1) are the Dyck paths with area n between the x-axis and the path which return to the x-axis only once (at their end), whereas A143951 includes paths with intercalated touches of the x-axis. - R. J. Mathar, Aug 22 2018
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..10000 (terms 0..1000 from Joerg Arndt)
A. M. Odlyzko and H. S. Wilf, The editor's corner: n coins in a fountain, Amer. Math. Monthly, 95 (1988), 840-843.
FORMULA
a(0) = 1 and a(n) = abs(A049346(n)) for n>=1.
G.f.: 1/ (1-q/(1+q/ (1+q^2/(1-q^2/ (1-q^3/(1+q^3/ (1+q^4/(1-q^4/ (1-q^5/(1+q^5/ (1+-...) )) )) )) )) )).
G.f.: 1 + q * F(q,q) where F(q,y) = 1/(1 - y * q^2 * F(q, q^2*y) ); cf. A005169 and p. 841 of the Odlyzko/Wilf reference; 1/(1 - q * F(q,q)) is the g.f. of A143951. - Joerg Arndt, Mar 09 2014
G.f.: 1 + q/(1 - q^3/(1 - q^5/(1 - q^7/ (...)))) (from formulas above). - Joerg Arndt, Mar 09 2014
G.f.: F(x, x^2) where F(x,y) is the g.f. of A239927. - Joerg Arndt, Mar 29 2014
a(n) ~ c * d^n, where d = 1.23729141259673487395949649334678514763130846902468... and c = 0.0773368373684184197215007198148835507944051447907... - Vaclav Kotesovec, Sep 05 2017
G.f.: A(x) = 2 -1/A143951(x). - R. J. Mathar, Aug 23 2018
EXAMPLE
From Joerg Arndt, Mar 08 2014: (Start)
The a(21) = 7 rough sandpiles are:
:
: 1: [ 1 2 1 2 1 2 1 2 1 2 3 2 1 ] (composition)
:
: o
: o o o o ooo
: ooooooooooooo (rendering of sandpile)
:
:
: 2: [ 1 2 1 2 1 2 1 2 3 2 1 2 1 ]
:
: o
: o o o ooo o
: ooooooooooooo
:
:
: 3: [ 1 2 1 2 1 2 3 2 1 2 1 2 1 ]
:
: o
: o o ooo o o
: ooooooooooooo
:
:
: 4: [ 1 2 1 2 3 2 1 2 1 2 1 2 1 ]
:
: o
: o ooo o o o
: ooooooooooooo
:
:
: 5: [ 1 2 3 2 1 2 1 2 1 2 1 2 1 ]
:
: o
: ooo o o o o
: ooooooooooooo
:
:
: 6: [ 1 2 3 2 3 4 3 2 1 ]
:
: o
: o ooo
: ooooooo
: ooooooooo
:
:
: 7: [ 1 2 3 4 3 2 3 2 1 ]
:
: o
: ooo o
: ooooooo
: ooooooooo
(End)
From Joerg Arndt, Mar 09 2014: (Start)
The A097331(9) = 14 such sandpiles with base length 9 are:
01: [ 1 2 1 2 1 2 1 2 1 ]
02: [ 1 2 1 2 1 2 3 2 1 ]
03: [ 1 2 1 2 3 2 3 2 1 ]
04: [ 1 2 1 2 3 2 1 2 1 ]
05: [ 1 2 1 2 3 4 3 2 1 ]
06: [ 1 2 3 2 1 2 3 2 1 ]
07: [ 1 2 3 2 1 2 1 2 1 ]
08: [ 1 2 3 2 3 2 1 2 1 ]
09: [ 1 2 3 2 3 2 3 2 1 ]
10: [ 1 2 3 4 3 2 1 2 1 ]
11: [ 1 2 3 2 3 4 3 2 1 ]
12: [ 1 2 3 4 3 2 3 2 1 ]
13: [ 1 2 3 4 3 4 3 2 1 ]
14: [ 1 2 3 4 5 4 3 2 1 ]
(End)
PROG
(PARI) N = 66; q = 'q + O('q^N);
G(k) = if(k>N, 1, 1 + (-q)^(k+1) / (1 - (-q)^(k+1) / G(k+1) ) );
gf = 1 / G(0);
Vec(gf)
(PARI)
N = 66; q = 'q + O('q^N);
F(q, y, k) = if(k>N, 1, 1/(1 - y*q^2 * F(q, q^2*y, k+1) ) );
Vec( 1 + q * F(q, q, 0) ) \\ Joerg Arndt, Mar 09 2014
CROSSREFS
Cf. A049346 (g.f.: 1 - 1/G(0), where G(k)= 1 + q^(k+1) / (1 - q^(k+1)/G(k+1) ) ).
Cf. A226728 (g.f.: 1/G(0), where G(k) = 1 + q^(k+1) / (1 - q^(k+1)/G(k+2) ) ).
Cf. A226729 (g.f.: 1/G(0), where G(k) = 1 - q^(k+1) / (1 - q^(k+1)/G(k+2) ) ).
Cf. A006958 (g.f.: 1/G(0), where G(k) = 1 - q^(k+1) / (1 - q^(k+1)/G(k+1) ) ).
Cf. A227309 (g.f.: 1/G(0), where G(k) = 1 - q^(k+1) / (1 - q^(k+2)/G(k+1) ) ).
Sequence in context: A059779 A291874 A049346 * A291905 A347584 A366398
KEYWORD
nonn
AUTHOR
Joerg Arndt, Jul 06 2013
STATUS
approved